It's used to treat disorders and diseases (8)
I believe the answer is:
medicine
'it's used to treat disorders and diseases' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for medicine that I've seen before include "It's taken to treat disease" , "The practice of diagnosis and treatment of disease" , "an answer to all clues, initially" , "It treats, prevents or alleviates disease" , "Curative drug" .)